Technical Abstract:
In order to better understand fiber digestion in the pig, two types of selective enrichments to isolate cellulose, xylan and pectin utilizing bacteria, were used. Rapid flow isolations utilized a chemostat with a flow rate of 25%/h combined with substrate immobilized in Dacron bags. Substrate depleted isolations utilized substrate depleted rumen fluid medium as a base with single carbohydrate additions. Both methods used carbohydrate specific agars to assist in bacterial isolations. A total of 332 isolates were recovered using the rapid flow isolation method while 59 were recovered from the substrate depleted method. All isolates had approximately 700 bp of 16S rRNA genes initially sequenced. Based on initial sequence groupings, 150 isolates had nearly full 16S rRNA genes sequenced resulting in 87 unique sequences. Isolates which had both low sequence similarity to cultured bacteria and those which were closely related to more than one bacterium were biochemically characterized. Bacteria with the genera classification Clostridium were isolated with the highest frequency, 24.1% of isolates, followed by 11.5% Lactobacillus, 11.5% Enterococcus and 9.2% Escherichia. Isolates most closely related to uncultured sequences comprised 6.9% of total isolates. Clostridium species were most often isolated from cellulose and pectin while Lactobacillus species were most frequently isolated from xylan. These isolates will be used to gain a better understanding of fiber digestion in the pig.